Though my tree dahlia is 13' tall, it has nary a bud. It really does not get enough sun and yes, it probably could use a dose of fertilizer. So far, it has not been nipped by Jack Frost.
Angela's tree dahlia is only about 10' tall but has this lovely, lovely bloom plus many more buds. Her's does get more sun but did get nipped by Jack Frost in spite of being next to her warm stucco flavored house. Go figure!